This invention relates to carburetor assemblies for internal combustion engines each comprising a main carburetor for producing dilute fuel-air mixtures and an auxiliary carburetor for producing enriched fuel-air mixtures, and more particularly to a carburetor assembly of the type described which is provided with means for effecting control of the ratio of the volume of an enriched fuel-air mixture supplied to the engine from the auxiliary carburetor to the volume of a dilute fuel-air mixture supplied to the engine from the main carburetor or the so-called air ratio.
In order to avoid the problem of air pollution by noxious components of exhaust gases from internal combustion engines, the internal combustion engines of automotive vehicles are nowadays provided with a main combustion chamber, and an ignition chamber communicating with the main combustion chamber and having an ignition plug mounted therein. In such internal combustion engines, dilute fuel-air mixtures are supplied to the main combustion chamber and enriched fuel-air mixtures are supplied to the ignition chamber, and each enriched fuel-air mixture is ignited in the ignition chamber to produce a flame which advantageously ignites each dilute fuel-air mixture in the main combustion chamber so that the engine can operate smoothly by the combustion of dilute fuel air mixtures for the most part of the duration of its operation. Carburetor assemblies used with such internal combustion engines each comprises a main carburetor for supplying dilute fuel-air mixtures to the main combustion chamber, and an auxiliary carburetor for supplying enriched fuel-air mixtures to the ignition chamber.
In conventional carburetor assemblies, it has hitherto been customary to manually effect control of the throttle valve of the auxiliary carburetor at the time the engine is started, although the throttle valve of the auxiliary carburetor is coupled to the throttle valve of the main carburetor to operate conjointly therewith when the engine is in steady state operating condition. More specifically, during the period in which the engine is started, self-cranking is attained so that the engine can carry on its motion by its own power and warming-up of the engine is completed, it has been usual practice to manually control the degree of opening of the throttle valve of the auxiliary carburetor in such a manner that the ratio of the volume of an enriched fuel-air mixture supplied from the auxiliary carburetor to the volume of a dilute fuel-air mixture supplied from the main carburetor is higher during the aforesaid period than during the period of steady state operation of the engine. Some disadvantages are associated with this manual control system. When control is effected manually, changes in the ratio of the volume of an enriched mixture to the volume of a dilute mixture is discontinuous, with the result that the operating condition of the engine becomes unstable. This leads to an increase in the amounts of noxious components of exhaust gases from the engine.